<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style type="text/css">
      h1 {
        color: red;
      }
      button {
        cursor: pointer;
        width: 108px;
        height: 44px;
        line-height: 45px;
        line-height: 44px\9;
        padding: 0;
        background: 0 0;
        background-color: #4e6ef2;
        border-radius: 0 10px 10px 0;
        font-size: 17px;
        color: #fff;
        box-shadow: none;
        font-weight: 400;
        border: none;
        outline: 0;
      }
      kfm {
        color: green;
      }

      .element::before {
        content: ""; /* 内容, 必须有这个属性 */
        width: 20px;
        height: 20px;
        background: red; /* 颜色 */
        display: inline-block;
      }
      .element::after {
        content: "开发喵♥"; /* 内容, 必须有这个属性 */
        color: red; /* 颜色 */
        font-size: 20px; /* 字体大小 */
      }
    </style>
    <link rel="stylesheet" href="style.css" />
  </head>
  <body>
    <h1 style="color: yellow">一级标题</h1>
    <h1>一级标题2</h1>
    <h1 class="element">一级标题3</h1>
    <h2>二级标题</h2>
    <button>百度一下</button>

    <kfm>开发喵</kfm>
  </body>
</html>
